In Japanese Patent Application No. 2004-186312, the inventors proposed to provide a buffer in an overhead space on a side of a traveling rail of an overhead traveling vehicle. In the overhead traveling vehicle system, the overhead traveling vehicle is provided with a lateral movement unit for moving an elevation drive unit to move laterally with respect to the traveling rail such that the article is transferred to/from the side buffer. In this respect, the inventors studied to further increase the storage capacity of the side buffer, and achieved the present invention.